Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center

 
 

 

Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Accomplishments
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
 
Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0742Z May 15, 2019)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
342 AM EDT Wed May 15 2019

Valid 12Z Wed May 15 2019 - 12Z Sat May 18 2019

...Western U.S....

As an anomalously deep upper low/trough moves across the region,
winter is forecast to return to portions of the Sierra, Great
Basin and northern Rockies.

Overall, models are in good agreement showing an upper low closing
off over the eastern Pacific Wednesday night before moving inland
near the California-Oregon border on Thursday.  As it moves inland
on Thursday, this anomalously deep system is expected to carve out
500mb heights more than 2 standard deviations below normal across
much of northern and central California.  At the onset of
precipitation, snows levels will be high - initially confining the
threat for heavy accumulations to areas above 8,000 ft.  WPC
guidance for Day 1 (ending 12Z Thursday) indicates a Slight Risk
for accumulations of a foot or more for portions of the central
Sierra above 8,000 ft. 

As the system moves inland, snow levels will drop significantly
along the Sierra into the Great Basin on Thursday.  WPC guidance
on Day 2 (ending 12Z Friday) shows a Slight Risk for accumulations
of a foot or more for areas as low 5,000 ft along the western
slopes of the central and southern Sierra, with a Moderate Risk
for areas above 7,000 ft.  Significant snow accumulations are
possible farther east across the higher elevations of the Great
Basin, with WPC guidance indicating a Slight Risk or greater for
accumulations of 4-inches or more across the central Nevada ranges.

As the upper low/trough pivots to the northeast, snows will
diminish across California and Nevada while developing farther to
the north across portions of the northern Rockies Friday into
early Saturday.   Increasing upper divergence coupled with low
level convergence and southwesterly inflow will support widespread
precipitation across the region.  With snow levels falling as the
upper low lifts north, the potential for locally heavy
accumulations will increase Friday into early Saturday across
portions of the central Idaho, northwestern Wyoming and
southwestern Montana ranges.

The probability of significant icing is less than 10 percent.

Pereira